Re: True Air Speed?

Date:         01 Feb 99 02:36:53 
From:         av8rmike@aol.com (AV8RMike)
Organization: AOL http://www.aol.com
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>Can anyone tell me how to work out TAS for IAS?
>What other info is required?

IAS corrected for instrument error = CAS (calibrated), corrected for
compressibility = EAS (equivilant), corrected for altitude & temp = TAS.

The difference between IAS and CAS & EAS, is usually pretty small.

There are several rough rules of thumb, I used the fisrt one:

True Airspeed

Example conditions:	Altitude 35,000',
		IAS 280 knots
		TAT -15°C

Altitude (1,000's) x 6	35 x 6 = 210
+IAS		210 + 280 = 490
+ TAT		490 + (-15) = 475 KTAS

		OR

For every 5,000' increase 10%
Altitude ÷ 5		35,000 = 7
x IAS		.7 x 280 = 196
+IAS		196 + 280 = 476 KTAS

		OR

Altitude (1,000's) x 2		35 x 2 = 70
Take result as % of IAS	.70 x 280 = 196
+ IAS			196 + 280 = 476 KTAS

		OR

IAS x 2%			280 x .02 = 5.6
x Altitude (1,000's)		5.6 x 35 = 196
+IAS			196 + 280 = 476 KTAS

Again these are very rough, but they work for basic number crunching in your
average jet airliner.  For more accurate numbers, I use an ASA Pathfinder or
other aviation calculator.